1. Field of the Invention
The present invention generally relates to signal processing for apparatuses such as television signal receivers, and more particularly, to an apparatus and method for performing signal processing that is capable of removing adjacent channel energy for extremely different desired channel bandwidths and varying adjacent channel conditions.
2. Background Information
With apparatuses such as television signal receivers, the proper reception of a desired channel may be adversely affected by the presence of undesired adjacent channels. One example of this adjacent channel problem may be observed with the so-called “Open Cable” standard. In particular, the Open Cable standard refers to the Society of Cable Telecommunications Engineers (SCTE) 28 standard which combines certain physical layer aspects of the SCTE 55-1 and SCTE 55-2 standards. The aforementioned standards are generally known to those skilled in the art.
One problem with combining the SCTE 55-1 and SCTE 55-2 standards relates to bandwidth differences in the physical layer of an out-of-band channel (also known as a forward data channel). In particular, there is a 2:1 difference in bandwidth between the high and low bandwidth signals used in these two standards. This bandwidth difference is largely attributable to the fact that the SCTE 55-1 and SCTE 55-2 standards use three extremely different symbol rates, namely: 0.772 MSym/S, 1.024 MSym/S, and 1.544 MSym/S. Each one of these symbol rates uses a different bandwidth, and thereby produces a different adjacent channel condition during signal processing.
Conventionally, a surface acoustic wave (SAW) filter or other high order filter is used before analog-to-digital conversion to remove adjacent channel energy. However, if the adjacent channel energy is not sufficiently removed, poor decisions in symbol timing and carrier recovery as well as equalization may result, thereby causing demodulation errors.
Heretofore, the aforementioned problem of removing undesired adjacent channel energy has not been adequately addressed. Accordingly, there is a need for an apparatus and method capable of removing adjacent channel energy for extremely different desired channel bandwidths and varying adjacent channel conditions. The present invention addresses these and/or other issues.